In the case of piston cylinders, cylinder housings either having a smooth outer surface or provided with cooling fins can be used. With respect to the type with smooth housings, it is not likely that foil-type valves are used because of the absence of the contact surface necessary for foils. Therefore, usually disk valves are installed which are more expensive and whereby, a lesser efficiency of the compressor has to be accepted. Aside from that, disk valves are only suitable for compressors with low to medium rotational speed.
In some of the presently known compressor piston cylinder heads, such parts as the cylinder housing, the valve plate, and the cylinder head are cast in one piece. Since this arrangement requires that the cylinder head be open for installation of the foils, a cylinder head cover, having an intake connection is used as a valve seat for the intake valve and as a valve stop for the discharge valve. Such a cylinder head cover is equipped with cross pieces and hollow spaces forming the intake chamber, the discharge chambers, and the cooling chambers, so that a number of sealing gaskets are necessary between the discharge chambers and the cooling chambers, as well as between the chambers and atmosphere. Said sealing gaskets are located on several surfaces of the cylinder head according to the situations in which sealing problems exist.